There are various types of posture adjusting devices for appropriately adjusting the posture of an occupant seated in a vehicle seat. Many of them use air cushions as actuators and adjust the pressure in the air cushions under feedback control by monitoring the outputs from pressure sensors configured to detect the pressure in the air cushions (see JPH6-286508A and JP2010-115474A, for example). The pressing by the air cushions can be controlled finely through selection of sizes and positions of the air cushions and adoption of various types of air pressure control. However, the pressure in the air cushion that is monitored is not directly related to the actual feeling of the occupant; namely, the control is conducted based on indirect physical quantities instead of actual sensory indices.
The occupant posture adjusting device (vehicle seat control device) disclosed in JPH6-286508A includes a seat reclining mechanism for adjusting an angle of a seat back of a seat, a reclining sensor for detecting an angle of the seatback, first and second air cushions respectively disposed in an upper part and a lower part of the seat back, first and second pressure control units (solenoid valves) for respectively controlling the internal pressures of the first and second air cushions, first and second pressure sensors for respectively detecting the internal pressures of the first and second air cushions, a first storage unit storing seat back control data defining a prescribed correlation between the angle of the seat back and the ratio of the internal pressures of the first and second air cushions, and an operation control unit configured to control the seat reclining mechanism according to the output signals of the first and second pressure sensors or to control the first and second pressure control units according to the output signal from the reclining sensor so as to satisfy the prescribed correlation defined by the seat back control data. The vehicle seat control device disclosed in JPH6-286508A further includes a seat slide mechanism for adjusting the position of the seat in the fore and aft direction, a slide sensor for detecting the position of the seat, third and fourth air cushions disposed in a seat cushion to respectively support buttocks and thighs of an occupant seated in the seat, third and fourth pressure control units for respectively controlling the internal pressures of the third and fourth air cushions, third and fourth pressure sensors for respectively detecting the internal pressures of the third and fourth air cushions, and a second storage unit storing seat cushion control data defining a prescribed correlation between the fore-and-aft position of the seat and the ratio of the internal pressures of the third and fourth air cushions, wherein the operation control unit controls the seat slide mechanism according to the output signals of the third and fourth pressure sensors or controls the third and fourth pressure control units according to the output signal from the slide sensor so as to satisfy the prescribed correlation defined by the seat cushion control data. The vehicle seat control device disclosed in JPH6-286508A further includes a front vertical mechanism for adjusting the height of the front end portion of the seat and a rear vertical mechanism for adjusting the height of the rear end portion of the seat, and the operation control unit may control the front and rear vertical mechanisms in addition to the seat slide mechanism according to the output signals of the third and fourth pressure sensors to satisfy the prescribed correlation defined by the seat cushion control data.
JP2010-115474A (also published as US2010/0117414A1) discloses an intelligent vehicle seat support system capable of automatically providing a passenger with a seat form suitable for the passenger although the passenger does not directly control the seat support system. The vehicle seat support system disclosed in JP2010-115474 includes an air storage tank for storing air and supplying the air when needed, a plurality of air cushions disposed in a vehicle seat in contact with a human body, and configured to selectively expand and shrink depending on the air flow, a pressure sensor for measuring air pressure of each air cushion, an air control valve disposed between the air storage tank and the air cushions, and configured to control the air that flows into each of the air cushions, and a control unit for, when a passenger takes the vehicle seat, automatically controlling the air control valve so that it starts injecting air into each of the air cushions, and, when the air pressure of each air cushion is higher than a preset reference value, controlling the air control valve so that it stops injecting air into each air cushion. In the intelligent vehicle seat support system disclosed in JP2010-115474A, the pressure difference between a left-side of the air cushions and a right-side of the air cushions may be determined, and, if the pressure difference exceeds the second preset reference value and the time duration during which the pressure difference is maintained exceeds the preset time period, the posture of the passenger is determined to have changed.
In occupant posture adjusting devices using air cushions, there is a large degree of freedom in arrangement of the air cushions, and it is relatively easy to incorporate many air cushions in the seat back to localize an area pressed by each air cushion. However, if a high pressing force is applied to a narrow area of the body of the seated occupant, it would cause discomfort to the occupant.
JP2017-81361A (also published as US2018/0304786A1) discloses a vehicle seat including a support mechanism for pressing and supporting a seated occupant's back. The vehicle seat disclosed in JP2017-81361A includes a seat cushion on which an occupant is seated, and a seat back on which the back of the occupant seated on the seat cushion reclines. The seat back includes a urethane pad having its surface covered with a trim cover, and a pressing device having a resin plate for supporting a part of the urethane pad, a laterally extending shaft, and press members arranged at upper and lower sides in a longitudinal direction with respect to the shaft at the back side of the urethane pad surface covered with the trim cover. The laterally extending shaft of the pressing device is rotated or oscillated in one direction so that the press member at the upper side presses an upper part of the urethane pad forward via the resin plate. The laterally extending shaft of the pressing device is rotated or oscillated in a direction opposite to the one direction so that the press member at the lower side presses a lower part of the urethane pad forward via the resin plate. Thereby, the mechanism unit for pressing and supporting the lumbar and the pelvis of the occupant seated on the vehicle seat may be simply configured with fewer components.